As the image sensor and optical technology progress, hand-held devices and small sized optical applications become popular. Further, with the development of higher performance cellular phones and portable cameras, small sized image modules and lens systems with high optical quality are currently under development. Especially, advances of image sensors in the field of miniaturization and highly dense pixels increase the need optical module or lens system with high resolution performance and more compactness. Due to the optical configuration and constraints, the size of hand-held devices has limitation to become smaller.
In response to such needs, a small number lens construction may be used in order to satisfy the requirements of compactness and low cost. Because of the constraint of small number of optical lenses, aspheric surface design becomes popularly spread in order to achieve higher performance.
In the present invention, by introducing a lens-surfaced prism, the size in thickness is considerably reduced while the optical path length of the lens system remains the same or longer. The compact image taking lens system with a lens-surfaced prism of the present invention has many advantages over the prior arts in the field of invention, such as compactness in thickness, small number of optical elements, higher performance of optical quality, enough space for optional elements such as infrared cut-off filter and diversity in optical geometry.